A passive optical network (PON) can deliver voice, video and other data among multiple network nodes using a common optical fiber link. Passive optical splitters and combiners enable a number of network nodes to share the optical fiber link. Each network node terminates the optical fiber link for a residential or business subscriber, and is sometimes referred to as a subscriber premises node. A PON typically includes a PON interface having multiple, independent PON interface modules that serve multiple optical fiber links. In the case of data services, the PON interface receives data packets from an Internet service provider for transmission to network nodes. A PON interface module provides an Ethernet interface for transmission and reception of over a particular optical fiber link that serves a group of network nodes.
A group of network nodes ordinarily forms a subnet for purposes of IP addressing. In particular, a PON interface module typically carries a class C network address. Consequently, the group of network nodes served by a PON interface module consumes an entire subnet scope of IP addresses. Unfortunately, the number of network nodes served by a given PON interface module may be much less than the number of available addresses within the subnet scope, e.g., 255 addresses. Dedication of an entire subnet scope to a single PON interface module therefore results in wasted IP addresses, i.e., addresses that are not used within the group of network nodes. Moreover, an Internet service provider (ISP) must allocate an entire subnet to each PON interface module, which can be expensive.